Younger generations may be aging faster than their predecessors, and this may be linked to a rise in early-onset cancers, a new study suggests.There have been recent increases in the rates of some cancers among adults under 50, including breast, colorectal, kidney and uterine cancers. One 2023 paper suggests that these early-onset cancer diagnoses rose by 25% globally between 1990 and 2019, and scientists are still investigating why."The trend of increased cancers at younger ages is very real, and it is not simply because of more efficient diagnosis, or diagnosis at earlier stages," said Dr. Jyoti Nangalia, a hematologist and cancer researcher at the Wellcome Sanger Institute in the U.K. who was not involved in the new study. "It is possible that we are being exposed to new cancer-causing risks or that [our] defences to them are somehow altered," she told Live Science in an email.The new study, published June 22 in the journal Nature Medicine, suggests that younger generations may have a wider "gap" between their chronological ages and their biological ages a measurement of how quickly the body's tissues and systems are aging than older generations do. The greater gap among younger adults seems to be linked with a higher risk of developing cancer early in life.The new study cannot prove that faster biological aging causes early-onset cancer, but it provides new clues for scientists trying to unpack what might be driving the worrying trend."This is really proof-of-concept," study co-author Yin Cao, a molecular and clinical epidemiologist at the Washington University School of Medicine and Siteman Cancer Center, told Live Science.Concerning trends lurking in dense dataChronological age is straightforward: It's the number of years that have passed since a person's birth. "Biological age," however, can vary wildly from one person to another. This catch-all term describes a range of metrics, including markers on DNA and in the bloodstream. These are often measured using "aging clocks," which aim to determine if the body is acting much older than its chronological age. Scientists have increasingly used these summary measures in an attempt to understand why some people are more prone to age-related diseases than others. To check whether there could be a link between biological age and the rise in early cancers, the new study analyzed data from more than 150,000 adults in the UK Biobank, a long-running project that has been tracking the health of about half-a-million U.K. adults since the mid2000s. The participants had provided blood samples, with many already measured for markers used to track biological aging. The study authors plugged these results into PhenoAge, a statistical model that estimates a person's "age gap" at a given chronological age. In essence, this model can compare snapshots of two 40-year-olds one born in 1950 and the other in 1965 and see if their blood markers suggest they're the same biological age."The traditional approach is really focusing on individual risk factors" for cancer, such as a history of obesity or a high intake of ultraprocessed foods, Cao said. "We are testing whether we can leverage these large biobanks and potentially find some biological imprint as a potential reflection of many exposures that can be linked with cancer risk," she said. The analysis revealed a concerning pattern: UK Biobank participants born between 1965 and 1974 had a larger age gap than those born between 1950 and 1954 at the same chronological ages. Based on PhenoAge's metrics, the younger cohort had systemic aging levels about 0.23 standard deviations higher than the older cohort a modest shift toward older-looking biology. The researchers applied this same approach to about 10,000 participants in the U.S. National Institutes of Health's All of Us Research Program, another large biobank. There, they found a more pronounced pattern: People born between 1990 and 1999 had age gaps about 0.92 standard deviations higher than those born between 1965 and 1969.Another blood-based aging clock, called the Klemera-Doubal method, showed broadly similar patterns to PhenoAge, albeit slightly weaker ones, the study found.One type of cancer that's on the rise in adults under 50 is breast cancer. (Image credit: kali9 via Getty Images)Real trend or data mirage?In the UK Biobank cohort, the researchers found that participants with higher age gaps were more likely to develop early-onset solid cancers, meaning cancerous tumors that appear in tissues, rather than "liquid" cancers present in bodily fluids. This link was strongest for lung, gastrointestinal and uterine cancers. This finding was based on the patients' medical records. When the participants were divided into three groups based on their biological ages, those in the highest group had a roughly 15% higher risk of early-onset solid cancer than those in the lowest group.To probe deeper, the authors used a different model that estimates biological aging at the level of specific organs and systems, using patterns of proteins in the blood. In almost 20,000 UK Biobank participants, they found that markers suggesting an "older-than-expected" immune system were linked with a higher risk of early-onset lung cancer. Similarly, markers suggesting older-than-expected fat tissue were linked with a higher risk of early-onset colorectal cancer.Does this mean younger generations are aging faster and that's causing the rise in cancers? Maybe, but maybe not there are important caveats to the study's findings. The patterns will need to be confirmed in other datasets and populations, Cao noted. Biological aging tests, including PhenoAge, are also relatively new, and their implications aren't fully understood. While they clearly capture something about health and risk at the population level, at the individual level, different biological age tests can give very different answers for the same person. That raises questions about what any single score really means for individual health. It may be that the differences PhenoAge uncovered between younger and older people have to do with how the test was originally calibrated, Stephen Burgess, a professor of biostatistics at the University of Cambridge who was not involved in the study, told Live Science in an email. To know if that's the case, one would have to dig deeper into how PhenoAge scores are calculated and see if that might have skewed its assessment of the UK Biobank and All of Us cohorts, he said.Related storiesMore young people are getting colorectal cancer here's what scientists think might be happeningBiological aging may not be driven by what we thoughtNew 'biological aging' test predicts your odds of dying within the next 12 monthsCao added that, while PhenoAge scores have been tied to mortality risk across a range of adults, the test "requires further validations" when it comes to assessing cancer risk. As with any observational study using large databases, it is hard to untangle cause and effect, Nangalia added. "The main issue for this paper is one of correlation versus causality," she said. "Either way, it is useful with the first, as a potential way of tracking population health and cancer risk, and with the second, as insights into cancer-causing mechanisms." Cao hopes her team's approach will serve as another useful tool to figure out why more young people are getting cancer. " Hopefully this is just a starting point," Cao said.